package com.hmdp.utils;

import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;

/**
 * 全局唯一ID生产器
 */
@Component
public class RedisIdWorker {
    /**
     * 开始时间戳
     */
    private static final long BEGIN_TIMESTAMP = 1640995200l;
    //序列号的位数
    private static final int COUNT_BITS = 32;
    private StringRedisTemplate stringRedisTemplate;

    public RedisIdWorker(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    public long nextId(String keyPrefix){
        //1、生成时间戳
        LocalDateTime now = LocalDateTime.now();
        long nowSecond = now.toEpochSecond(ZoneOffset.UTC);
        long timestamp = nowSecond - BEGIN_TIMESTAMP;

        //2、生成序列号
        //2.1 获取当前日期，精确到天
        String date = now.format(DateTimeFormatter.ofPattern("yy:MM:dd"));
        //2.2 自增长
        long count = stringRedisTemplate.opsForValue().increment("icr:" + keyPrefix + ":" + date);

        //3、拼接并返回
        //先将时间戳往前移动32位，然后通过 或运算 拼接序列号
        return timestamp << COUNT_BITS | count;
    }
}
